1. Field of the Invention
The present invention relates to a lens and an optical system including the lens, and an optical device including the lens.
2. Description of the Related Art
Conventionally, there have been well known: an optical elements that uses a light wave or electromagnetic wave; optical systems such as an image pickup optical system, an observation optical system, a projection optical system, and a signal processing system; and an optical device that uses these systems. These optical systems have a defect that image resolution is limited because of diffraction that occurs due to undulation property of a light wave or electromagnetic wave.
Therefore, as a technique for achieving image formation which exceeds the diffraction limit, use of a negative refractive index medium is disclosed in the following non-patent documents 2 and 5, etc.
FIG. 10 is a view for explaining an example of a technique for achieving such image formation. This figure shows image formation using a parallel flat plate 380 formed of a negative refractive index medium 301. In FIG. 10, t0 denotes a distance between an object point and a left side face of the flat plate 380; t0, denotes a distance between an image point and a right side face of the flat plate 380; “t” denotes a thickness of the flat plate 380; “i” denotes an incident angle; “r” denotes a refraction angle; and ns denotes a refractive index of the negative refractive index medium 301 with respect to a vacuum.
A refractive index of the periphery of the flat plate 380 with respect to a vacuum is n0, and n0=1 is established in the case of a vacuum. FIG. 1 shows a case in which n0=1 and ns=−1 are established.
The arrow indicates an emitted light component from among the light beams emitted from an object. Because a refraction law is established according to non-patent document 2, the following formula is established:n0 sin i=ns sin r  Formula 101
Assuming that n0=1 and ns=−1, the following formula is established:r=−i  Formula 102
Therefore, a light beam of the emitted light component is formed as an image point at a point at which t0′ satisfies the following formula:t0+t0′=t  Formula 103
On the other hand, an evanescent wave produced from an object point has intensity equal to that of the object point at a point at which t0′ satisfies Formula 103 as well. All the light beams emitted from the object point are collected at the image point, and thus, image formation exceeding the diffraction limit is achieved. This is referred to as complete image formation. It is known from non-patent document 2 listed below that, even if the periphery of the negative refractive index medium 301 is not a vacuum, complete image formation is achieved when Formula 103 and Formula 104 are satisfied:ns=−n0  Formula 104
Non-patent document 1: Mechanism and application of optical system, 73-77, 166-170, Optronics Co., Ltd., 2003
Non-patent document 2: J. B. Pendry Phys. Rev. Lett., Vol. 85, 18 (2000) 3966-3969
Non-patent document 3: M. Notomi Phys. Rev. B. Vol. 62 (2000) 10696
Non-patent document 4: V. G. Veselago Sov. Phys. Usp. Vol. 10, 509-514 (1968)
Non-patent document 5: L. Liu and S. He Optics Express Vol. 12 No. 20 4835-4840 (2004)
Non-patent document 6: Sato & Kawakami, Optronics, July, 2001, page 197
Patent document 1: US 2003/0227415 A1
Patent document 2: US 2002/0175693 A1